Various types of fluid pressure devices are known in which a pressure P within a chamber can be determined. One type of apparatus utilizes a sensor which can be elastically deformed, in which the elastic deformation or strain is sensed, the sensor being coupled to a pressure-sensitive device which provides an electrical output signal responsive to pressure exerted thereon. The strain-type element changes its dimension, and a previously existing bias pressure on the pressure transducer element changes, thus providing an output signal representative of pressure within the chamber.
A sensor suitable for sensing fluid pressure within a chamber, for example hydraulic pressure within a pump chamber, is described in U.S. Pat. No. 4,109,518, Dooley et al. This sensor is suitable for determining the hydraulic pressure available to inject fuel through the injection valve of a Diesel engine. The structure described includes a bolt which is screwed into the cylinder head of the internal combustion engine and which has a washer thereon, retaining a pressure-sensitive element in form of a piezo-ceramic disk, is secured to the cylinder head by means of a nut. The arrangement provides output signals which, however, are relatively small since the elastic deformation of the bolt or screw, which has a relatively large diameter, does not contribute to the deformation of the piezo-ceramic disk, and hence detracts from the signal amplitude.